US6761503B2 - Splined member for use in a slip joint and method of manufacturing the same - Google Patents

Abstract

An improved female splined member includes a female tubular member having an inner surface provided with a plurality of longitudinally extending grooves that are sized and spaced in accordance with a desired number and position of splines to be formed. A plurality of elongate rods is disposed in respective longitudinally extending grooves formed in the inner surface of the female tubular member. A quantity of positioning material is provided within spaces provided between the elongate rods and the longitudinally extending grooves. The positioning material is hardened to support the elongate rods in the longitudinally extending grooves to define a plurality of inwardly extending splines in the female splined member. An improved method for manufacturing a female splined member includes the initial step of providing a female tubular member having an inner surface provided with a plurality of circumferentially spaced, longitudinally extending grooves. Next, an elongate rod is provided in each of the longitudinally extending grooves in the female tubular member. Then, a quantity of positioning material is provided into spaces provided between the elongate rods and the longitudinally extending grooves in the female tubular member. Thereafter, the positioning material is allowed to harden.

Description

BACKGROUND OF THE INVENTION

This invention relates in general to slip joints, such as are commonly used in vehicle drive train systems, for transmitting rotational force or torque between telescoping members, while accommodating a limited amount of relative axial movement therebetween. In particular, this invention relates to an improved structure for a splined member that is adapted for use in such a slip joint.

In a typical land vehicle, a drive train system is provided for transmitting rotational power from an engine/transmission assembly to an axle assembly so as to rotatably drive one or more wheels of the vehicle. A typical drive train system includes a driveshaft assembly that is connected between an output shaft of the engine/transmission assembly and an input shaft of the axle assembly. To accomplish this, a first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft assembly, while a second universal joint is connected between a second end of the driveshaft assembly and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft assembly to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes thereof.

Not only must the drive train system accommodate a limited amount of angular misalignment between the engine/transmission assembly and the axle assembly, but it must also typically accommodate a limited amount of relative axial movement therebetween. A small amount of such relative axial movement frequently occurs when the vehicle is operated. To address this, it is known to provide a slip joint in the driveshaft assembly of the drive train system. A typical slip joint includes male and female telescoping members having respective pluralities of splines formed thereon. The male splined member has a plurality of outwardly extending splines formed on the outer surface thereof that cooperate with a plurality of inwardly extending splines formed on the inner surface of the female splined member. The cooperating splines of the male and female members provide a rotational driving connection through the slip joint, while permitting a limited amount of relative axial movement therebetween. The slip joint may be provided at the ends of the driveshaft assembly or in the interior thereof, as desired.

Conventional splined members are often formed by a machining process, wherein material is removed from a member to form splines therein. To accomplish this, the member is initially formed having a surface of predetermined size and shape. Then, a cutting tool (such as a hobbing tool) is moved into engagement with the surface of the member to remove some of the material therefrom. The material that remains on the member becomes the plurality of splines. As a result of this machining process, the splines are usually formed having relatively square faces, i.e., faces that are generally flat and extend generally radially relative to the rotational axis of the member. Then, the splined member is coated with a material having a relatively low coefficient of friction. The low friction coating is provided to minimize the amount of force that is required to effect relative movement between the two splined members. Also, the low friction coating provides a relatively tight fit between the cooperating splines of the two splined members, thus minimizing any undesirable looseness therebetween while continuing to allow free axial movement.

Although the above-described machining process for forming splines has functioned satisfactorily for many years, it has been found to be somewhat inefficient. This is because the machining process has been found to be relatively slow and expensive to perform. Also, the machining process results in a quantity of scrap material of which must be disposed. Thus, it would be desirable to provide an improved structure for a splined member for use in a slip joint and an improved method for manufacturing the same.

SUMMARY OF THE INVENTION

This invention relates to an improved structure and method for manufacturing a splined member for use in a slip joint for transmitting rotational force between two members, while accommodating a limited amount of relative axial movement therebetween. The splined member can include a female tubular member having an inner surface provided with a plurality of longitudinally extending grooves that are sized and spaced in accordance with a desired number and position of splines to be formed. A elongated rod is disposed in each of the longitudinally extending grooves formed in the inner surface of the female tubular member. A quantity of positioning material is provided within spaces provided between the elongated rods and the longitudinally extending grooves. The positioning material is then hardened to support the elongated rods in the longitudinally extending grooves to define a plurality of inwardly extending splines in the female splined member.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side elevational view of a vehicle drive train system including a slip joint in accordance with this invention.

FIG. 2 is an enlarged, exploded perspective view, partially broken away, of the slip joint illustrated in FIG.1.

FIG. 3 is a sectional elevational view of a hollow cylindrical member that can be used to formed a female splined member for the slip joint illustrated in FIGS. 1 and 2.

FIG. 4 is a sectional elevational view of the hollow cylindrical member illustrated in FIG. 3 after having a plurality of longitudinally extending grooves formed therein.

FIG. 5 is a sectional elevational view of a male positioning mandrel having a plurality of elongated rods supported thereon.

FIG. 6 is a sectional elevational view showing the male positioning mandrel and the elongated rods illustrated in FIG. 5 positioned concentrically within the hollow cylindrical member illustrated in FIG.4.

FIG. 7 is a sectional elevational view showing the female splined member that has been formed after a quantity of positioning material has been introduced by the male positioning member between the elongated rods and the longitudinally extending grooves of the hollow cylindrical member.

FIG. 8 is a sectional elevational view of the assembled slip joint illustrated in FIGS.1 and2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, there is illustrated in FIG. 1 a drive train system, indicated generally at10, in accordance with this invention. The illustrateddrive train system10, which is intended to be representative of any drive train system (vehicular or otherwise) for transferring rotational power from a source to a driven device, includes atransmission12 having an output shaft (not shown) that is connected to an input shaft (not shown) of anaxle assembly14 by adriveshaft assembly15. Thetransmission12 and theaxle assembly14 are conventional in the art. Thedriveshaft assembly15 includes a hollowcylindrical driveshaft tube16 that extends from a front end adjacent to thetransmission12 to a rear end adjacent to theaxle assembly14. Thedriveshaft assembly15 further includes a pair ofuniversal joints18 for rotatably connecting the output shaft of thetransmission12 to the front end of thedriveshaft assembly15 and for rotatably connecting the rear end of thedriveshaft assembly15 to the input shaft of theaxle assembly14. Theuniversal joints18 are also conventional in the art.

A slip joint, indicated generally at20, is provided for connecting the rear end of the frontuniversal joint18 to the front end of thedriveshaft tube16. The structure of theslip joint20 is illustrated in detail in FIG.2. As shown therein, theslip joint20 includes a female splined member, indicated generally at22, including a femaletubular member22ahaving a plurality of inwardly extending splines that are defined by a plurality of circumferentially spaced,elongated rods23. Theelongated rods23 extend radially inwardly from an inner surface of the femaletubular member22ato define the splines. The female splinedmember22 further has a pair of spaced apart yoke arms (not shown in FIG. 2) formed thereon that extend axially from the femaletubular member22aand are connected to the frontuniversal joint18. Thus, the female splinedmember22 is typically referred to as a slip yoke.

Theslip joint20 also includes a male member, indicated generally at24, that includes acylindrical body portion24ahaving a plurality of circumferentially spaced, longitudinally extendinggrooves24bformed in an outer surface thereof. A plurality ofballs25 are disposed in the longitudinally extendinggrooves24bformed in thecylindrical body portion24a. Theballs25 can be formed from a hardened, low-friction material, such as steel. Travel of theballs25 throughout thegrooves24bmay be limited by a mechanical stop or interference member, such as a cage generally indicated at19. Themale member24 further includes a reduceddiameter neck portion24cthat is secured to the forward end of thedriveshaft tube16 in a conventional manner, such as by welding. Thecylindrical body portion24aand theballs25 supported thereby are sized to fit telescopically within the splined end of the female splinedmember22 such that theelongate rods23 cooperate with theballs25 in respective longitudinally extendinggrooves24bto form theslip joint20. The telescoping nature of theslip joint assembly20 facilitates the installation of thedriveshaft assembly15 within a vehicle, accommodates relative axial movement between thetransmission12 and the axle assembly14 (such as might be caused by movement of the vehicle over rough terrain), and provides for some collapsibility of the driveshaft in the event of a collision of the vehicle.

Referring back to FIG. 1, atube yoke26 is provided for connecting the rear end of thedriveshaft tube16 to the rearuniversal joint18. Thetube yoke26 is conventional in the art and can be secured to the rearward end of thedriveshaft tube16 in any conventional manner, such as by welding. It will be appreciated that the female splinedmember22 may alternatively be provided at the forward end of thedriveshaft tube16 and the pair of spaced apart arms that are connected to the frontuniversal joint18 may extend axially from themale member24. It will also be appreciated that the slip joint20 may alternatively be provided for connecting the rear end of thedriveshaft tube16 to the rear universal joint18, and that thetube yoke26 may be provided for connecting the front end of thedriveshaft tube16 to the frontuniversal joint18. Alternatively, it will be appreciated that the slip joint20 may be provided in an intermediate or interior portion of thedriveshaft tube16, such as is commonly found in three joint driveshaft assemblies, wherein thedriveshaft tube16 is split into two driveshaft tube sections. Similarly, a number of other splined components are commonly used in conventional driveshaft assemblies, and the scope of this invention is intended to cover such other splined components.

Referring now to FIGS. 3 through 7, there is illustrated the steps in the method of this invention for forming the femalesplined member22 illustrated in FIG.2. Initially, a hollowcylindrical member30, as shown in FIG. 3, is provided. The hollowcylindrical member30 may be formed from any desired material, but is preferably formed from metallic material, such as steel or aluminum. Then, as shown in FIG. 4, the hollowcylindrical member30 is re-shaped by any conventional process to form thefemale tubular member22ahaving an inner surface provided with a plurality of circumferentially spaced, longitudinally extendinggrooves22b, as shown in FIG.4. The hollowcylindrical member30 can be re-shaped in this manner by any conventional process. For example, the hollowcylindrical member30 can be re-shaped by inserting a mandrel (not shown) into the hollowcylindrical member30 and then collapsing the hollowcylindrical member30 about the circumferential surface of the mandrel. The hollowcylindrical member30 can, for example, be collapsed in this manner using a magnetic pulse formation process. Thelongitudinally extending grooves22bare sized and spaced in accordance with a desired number and position of splines to be formed on the inner surface of thefemale tubular member22a.

Next, as shown in FIG. 5, a male positioning mandrel, indicated generally at40, is provided. Themale positioning mandrel40 includes an outer surface having a plurality of circumferentially spaced, longitudinally extendinggrooves40aprovided in the outer surface thereof. Similar to thegrooves22bdiscussed above, thegrooves40aare also sized and circumferentially spaced in accordance with a desired number and position of splines to be formed on the inner surface of thefemale tubular member22a. Next, anelongated rod23 is disposed in each of thelongitudinally extending grooves40aformed in the outer surface of themale positioning mandrel40. Theelongated rods23 can be formed from any desired material, but preferably are formed from a strong, rigid material, such as steel, to provide a hardened wear surface. Theelongated rods23 can be temporarily retained in thelongitudinally extending grooves40aby any conventional means. For example, theelongated rods23 can be temporarily retained in thegrooves40aby a mechanical retainer, such as a cage (not shown), adhesives, and the like. Alternatively, theelongated rods23 can be temporarily retained in thegrooves40asizingsuch grooves40ato frictionally engage and retain theelongated rods23 therein.

Themale positioning mandrel40 can further include a mechanism for injecting a quantity of a positioning material about theelongated rods23. The injecting mechanism can, for example, include a manifold, indicated generally at40b, that is provided in the interior of themale positioning mandrel40. The illustratedmanifold40bis an enlarged central bore that is formed through the interior of themale positioning mandrel40. The injecting mechanism can further include a plurality ofpassageways40cthat extend radially outwardly from the manifold40bto the outer surface of themale positioning mandrel40. In the illustrated embodiment, thepassageways40care axially and circumferentially spaced apart from one another and extend radially outwardly between adjacent ones of thelongitudinally extending grooves40aprovided in the outer surface of themale positioning mandrel40. However, thepassageways40cmay be oriented in any desired configuration. Lastly, the injecting mechanism can include one ormore channels40dformed in themale positioning mandrel40 through which coolant can flow. The purposes for the manifold40b, thepassageways40c, and thecoolant channels40dwill be explained below.

As shown in FIG. 6, themale positioning mandrel40 having theelongated rods23 supported thereon can be inserted concentrically within thefemale tubular member22a. When so positioned, the radially outermost portions of theelongated rods23 extend within the adjacent longitudinally extendinggrooves22bformed in thefemale tubular member22a. Themale positioning mandrel40 supports theelongated rods23 in this orientation while a quantity ofpositioning material50 is introduced between the outer surface of themale positioning mandrel40 and the inner surface of thefemale tubular member22a. Thepositioning material50 can, for example, be embodied as a hardenable liquid material that is introduced through the injecting mechanism described above. To accomplish this, thepositioning material50 is injected into the manifold40band radially outwardly through thepassageways40c. Alternatively, thepositioning material50 can be injected through thefemale tubular member22athrough ports (not shown) provided through thefemale tubular member22aor in any other manner.

When injected, thepositioning material50 fills the spaces between theelongate rods23 and thelongitudinally extending grooves22bin thefemale tubular member22a. Thepositioning material50 can also be injected into the annular spaces between the outer surface of themale positioning mandrel40 and the inner surface of thefemale tubular member22a, between adjacent ones of theelongated rods23. Thepositioning material50 can be embodied as any material that is suitable for retaining theelongated rods23 in thelongitudinally extending grooves22bprovided in the inner surface of thefemale tubular member22. For example, thepositioning material50 can be a molten plastic material that is filled or impregnated with glass or other reinforcing material. Thepositioning material50 can, if desired, be heated to facilitate flow thereof through the manifold40band thepassageways40c.

Once thepositioning material50 has been injected, it is caused to retain theelongated rods23 in thelongitudinally extending grooves22bprovided in the inner surface of thefemale tubular member22. This can be accomplished by causing thepositioning material50 to change from a liquid state to a solid state. This change of state can be achieved by allowing the hotliquid positioning material50 to cool and thereby solidify. Such cooling can be expedited by the passage of coolant through thecoolant channels40dformed in themale positioning mandrel40. In the illustrated embodiment, thepassageways40care sized to be relatively small in comparison with the manifold40b. This is desirable because it facilitates the separation of thepositioning material50 injected about theelongated rods23 from the positioning material that remains in thepassageways40c, thereby allowing easy removal of themale positioning mandrel40 from thefemale tubular member22bafter the injection process is completed.

Upon hardening, thepositioning material50 retains the elongatesrods23 in thelongitudinally extending grooves22bprovided in the inner surface of thefemale tubular member22a. After thepositioning material50 has hardened, themale positioning mandrel40 is removed, as shown in FIG.7. Theelongate rods23 remain in thelongitudinally extending grooves22bin thefemale tubular member22a, thereby forming a plurality of internal splines. Thus, thelongitudinally extending grooves22bneed not be precisely formed to conform closely to theelongated rods23, but rather need only be generally formed to allow thepositioning material50 to envelop theelongated rods23 and support them on thefemale tubular member22a. Thus, thepositioning material50 functions to both position theelongated rods23 and retain them in desired positions on thefemale tubular member22a. Thepositioning material50 can also function to physically insulate theelongated rods23 from thefemale tubular member22a. Consequently, thefemale tubular member22 and theelongate rods23 can be formed from dissimilar materials without being susceptible to undesirable galvanic corrosion. For example, thefemale tubular member22 can be formed from a relatively lightweight material, such as aluminum, while theelongated rods23 can be formed from a relatively heavier material, such as steel. Thepositioning material50 provides a barrier between the aluminum and steel to prevent the occurrence of galvanic corrosion.

After the femalesplined member22 has been manufactured in accordance with the method of this invention, the slip joint20 is assembled as shown in FIG.8. In this assembled condition, theballs25 are supported in theelongated grooves24bin thecylindrical body portion24aof themale member24 of the slip joint20. Thecage19 is provided about thecylindrical body portion24a. Thecage19 functions to retain theballs25 in a fixed relation to one another and limit the travel of theballs25 in theelongated grooves24bin themale member24. Themale member24 and theballs25 andcage19 supported by themale member24 are inserted into the femalesplined member22 so that theballs25 in each of theelongated grooves24bin themale member24 are disposed between two adjacentelongate rods23. Theballs25 engage or cooperate with theelongate rods23 in a circumferential direction (in a clockwise or counter-clockwise direction when viewing FIG. 8) to transmit torque or rotational force between the femalesplined member22 and themale member24. Moreover, the femalesplined member22 and themale member24 are telescopically displaceable relative to one another. Theballs25 facilitate unencumbered telescopic displacement between the femalesplined member22 and themale member24. As stated above, the telescoping nature of the slipjoint assembly20 facilitates the installation of thedriveshaft assembly15 within a vehicle, accommodates relative axial movement between thetransmission12 and theaxle assembly14, and provides for some collapsibility of the driveshaft in the event of a collision of the vehicle.

Although this invention has been described in the context of the illustrated femalesplined member22, it will be appreciated that the same general method can be used to form the malesplined member24, wherein theelongated rods23 are supported in grooves formed in the outer surface of thebody portion24aof the male splined member by thepositioning material50.

In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims (14)

What is claimed is:

1. A slip joint comprising:

a first member including a surface having a first plurality of grooves formed therein, a rod disposed in each of said first plurality of grooves, and a quantity of material extending between said first member and each of said rods for retaining said rods within said first plurality of grooves to define a plurality of splines on said first member that extend beyond said surface;

a second member including a surface having a second plurality of grooves formed therein; and

a plurality of balls disposed in each of said second plurality of grooves, said plurality of balls cooperating with said rods on said first member to provide a rotatable driving connection between said first and second members, while permitting relative axial movement therebetween.

2. The slip joint defined inclaim 1 wherein each of said first plurality of grooves extends longitudinally along said first member.

3. The slip joint defined inclaim 2 said rods are elongated and are disposed in said first plurality of longitudinally extending grooves.

4. The slip joint defined inclaim 1 wherein said material is disposed between said rods and said first member.

5. The slip joint defined inclaim 1 wherein said material is disposed between adjacent ones of said rods.

6. The slip joint defined inclaim 1 wherein said material is disposed between said rods and said first member and also between adjacent ones of said rods.

7. The slip joint defined inclaim 1 wherein said material is formed from a plastic material.

8. The slip joint defined inclaim 7 wherein said plastic material is impregnated with glass or other reinforcing material.

9. The slip joint defined inclaim 1 wherein said first member and said rods are formed from different materials.

10. The slip joint defined inclaim 1 wherein said first member is generally hollow and cylindrical in shape and includes an inner surface, and wherein said first plurality of grooves is formed in said inner surface.

11. The slip joint defined inclaim 10 wherein said second member is generally cylindrical in shape and includes an outer surface, and wherein said second plurality of grooves is formed in said outer surface.

12. The slip joint defined inclaim 1 wherein said first member is generally cylindrical in shape and includes an outer surface, and wherein said first plurality of grooves is formed in said outer surface.

13. The slip joint defined inclaim 12 wherein said second member is generally hollow and cylindrical in shape and includes an inner surface, and wherein said second plurality of grooves is formed in said inner surface.

14. The slip joint defined inclaim 1 further including a cage for retaining said balls in said first and second pluralities of grooves.

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